ktor android local http server throws error

user_140765 0
Viewed 1453

What did I do?

  1. Added dependencies under build.gradle
implementation "io.ktor:ktor:1.3.2"
implementation "io.ktor:ktor-server-netty:1.3.2"
implementation "io.ktor:ktor-gson:1.3.2"
  1. AndroidMenifest.xml
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.BLUETOOTH" />
  1. MainActivity.kt
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        embeddedServer(Netty, 9000) {
            install(ContentNegotiation) {
                gson {}
            }
            routing {
                get("/") {
                    call.respond(mapOf("message" to "Hello world"))
                }
            }
        }.start(wait = true)
    }
}

What went wrong?

Upon running app, I get following errors & android local server isn't starting.

No implementation found for int io.netty.channel.kqueue.Native.sizeofKEvent() 
(tried Java_io_netty_channel_kqueue_Native_sizeofKEvent 
and Java_io_netty_channel_kqueue_Native_sizeofKEvent__)

No implementation found for int io.netty.channel.epoll.Native.offsetofEpollData() 
(tried Java_io_netty_channel_epoll_Native_offsetofEpollData 
and Java_io_netty_channel_epoll_Native_offsetofEpollData__)
ktor kotlin httpserver localhost android
4 Answers

How did I fix it?

  1. Added dependencies under build.gradle
implementation "io.ktor:ktor:1.3.2"
implementation "io.ktor:ktor-server-jetty:1.3.2"
implementation "io.ktor:ktor-gson:1.3.2"

also

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}
defaultConfig {
    ...
    minSdkVersion 26
    ...
}
  1. AndroidMenifest.xml
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.BLUETOOTH" />
  1. MainActivity.kt
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        embeddedServer(Jetty, 9000) {
            install(ContentNegotiation) {
                gson {}
            }
            routing {
                get("/") {
                    call.respond(mapOf("message" to "Hello world"))
                }
            }
        }.start(wait = false)
    }
}
user_1407650

Netty's native transport doesn't support Android. You should probably try another Ktor engine, like CIO or Jetty.

user_7505100

I had the same issue. Change:

start(wait = true)

To:

start(wait = false)

And the Ktor server should be up and running on Android.

user_1294370
user_27383640
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